1. Field of the Invention
The present invention relates to a dental implant, and more particularly to an implant of the type which comprises a dental root to be embedded in a jaw bone alone or in combination with a dental crown or a dental crown support.
2. Description of Prior Arts
Hitherto there have been proposed various dental implants for replacing a lost tooth or lost teeth, and some of them have already been accepted for practical use. In many of these known dental implants, the basic material used for making the dental implant is metal or ceramics which is inactive in a living body. They are so designed as to be mechanically supported by the jaw bone. In other words, almost all of the known dental implants rely on a mechanical bonding force between the implant and the jaw bone. For this reason, the known dental implants are complicated in shape and are difficult to manufacture. In addition, they are apt to slip out due to the resorption of the jaw bone caused by the partial concentration of stress on a part thereof.
Recently it has been reported in the art that a very useful dental implant can be obtained by forming its dental root part with a biologically active material such as biologically active glass or glass-ceramics (cf. U.S. Pat. Nos. 4,159,358 and 4,234,972). Such biologically active material is able chemically to combine with bone. Therefore, if a dental implant is made of such biologically active material, then it is possible rigidly to fix the implant to the jaw bone without the need for mechanical bonding, and it enables simplification of the shape of the implant to a great extent.
However, the bonding strength between biologically active material and bone has a certain limit. Although the dental implant using a biologically active material can be designed to have a very simple form, there remains the possibility that the chemical bond between the implant and the bone may be broken and the implant may come out when a large stress is applied thereto by biting, for example, and the stress is concentrated on a limited portion of the dental implant.